<div dir="ltr">I guess the fact that different modes have fundamentally different APIs (e.g. GCM needs a MAC, CTR needs the counter, etc.) really points to that they should have different classes.<div><br></div><div>How about keysize, do we need a class for each?</div>
<div><br></div><div>Alex</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, Aug 7, 2013 at 5:12 PM, Donald Stufft <span dir="ltr"><<a href="mailto:donald@stufft.io" target="_blank">donald@stufft.io</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><br><div><div class="im"><div>On Aug 7, 2013, at 7:18 PM, Alex Gaynor <<a href="mailto:alex.gaynor@gmail.com" target="_blank">alex.gaynor@gmail.com</a>> wrote:</div>
<br><blockquote type="cite"><div dir="ltr">Another option is to compose them in the constructor: AES(keysize=256, mode=GCM) or so.<div><br></div><div>Alex</div></div></blockquote><div><br></div></div><div>We'd still essentially be passing AES-256-GCM into OpenSSL afaik. So afaik it'd only look like composing. We're not handling (most) of the differences between the modes (and none of the differences for key size).</div>
<div><br></div><div>The mode classes could be stuff that handles the slight differences in how you call the API (for instance GCM has an additional call to EVP_EncryptUpdate to give it the AAD and a different calls to handle getting the MAC data. I'm not sure how well that'd translate? It might work ok.</div>
<div><div class="h5"><br><blockquote type="cite"><div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, Aug 7, 2013 at 4:12 PM, Donald Stufft <span dir="ltr"><<a href="mailto:donald@stufft.io" target="_blank">donald@stufft.io</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div><br>
On Aug 7, 2013, at 6:32 PM, Jean-Paul Calderone <<a href="mailto:jean-paul@hybridcluster.com" target="_blank">jean-paul@hybridcluster.com</a>> wrote:<br>
<br>
> On 08/07/2013 06:16 PM, Donald Stufft wrote:<br>
>> So to kick things off I'd like to get AES-GCM exposed and figured it could be a good way to start the ball rolling for figuring out how we want to expose symmetric ciphers at the low level API.<br>
>><br>
>> I'm thinking cryptography.primitives.aes which has classes named like AES128GCM, AES256CBC, etc. The obvious naming scheme being AlgorithmKeysizeMode.<br>
>><br>
>><br>
><br>
> GCM (CBC, etc) is a mode of operation that is applicable to arbitrary<br>
> block ciphers.<br>
><br>
> Why should it be tied to "AES128"? Why wouldn't you GCM(AES128())? If<br>
> you're talking about primitives, AES128 is more primitive than GCM on<br>
> AES128. And GCM isn't specific to AES, so I don't see<br>
> cryptography.primitives.aes as the proper home for it.<br>
><br>
> I hope these aren't questions with highly obvious answers.<br>
<br>
</div></div>As far as I know (and I could be wrong? I don't know OpenSSL guts that well) OpenSSL doesn't do composition like that, in order to get AES-128-GCM you pass that in.<br>
<br>
Is there a way to access openssl where you're composing GCM with AES128? If not I think we'd be stuck do some sort of "combine variables of the classes AES128 and GCM to make the name AES-128-GCM to pass into openssl" thing which doesn't feel particularly clean to me?<br>
<div><div><br>
<br>
-----------------<br>
Donald Stufft<br>
PGP: 0x6E3CBCE93372DCFA // 7C6B 7C5D 5E2B 6356 A926 F04F 6E3C BCE9 3372 DCFA<br>
<br>
</div></div><br>_______________________________________________<br>
Cryptography-dev mailing list<br>
<a href="mailto:Cryptography-dev@python.org" target="_blank">Cryptography-dev@python.org</a><br>
<a href="http://mail.python.org/mailman/listinfo/cryptography-dev" target="_blank">http://mail.python.org/mailman/listinfo/cryptography-dev</a><br>
<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div dir="ltr">"I disapprove of what you say, but I will defend to the death your right to say it." -- Evelyn Beatrice Hall (summarizing Voltaire)<br>
"The people's good is the highest law." -- Cicero<br><div>GPG Key fingerprint: 125F 5C67 DFE9 4084</div></div>
</div>
_______________________________________________<br>Cryptography-dev mailing list<br><a href="mailto:Cryptography-dev@python.org" target="_blank">Cryptography-dev@python.org</a><br><a href="http://mail.python.org/mailman/listinfo/cryptography-dev" target="_blank">http://mail.python.org/mailman/listinfo/cryptography-dev</a><br>
</blockquote></div></div></div><div><div class="h5"><br><div>
<br>-----------------<br>Donald Stufft<br>PGP: 0x6E3CBCE93372DCFA // 7C6B 7C5D 5E2B 6356 A926 F04F 6E3C BCE9 3372 DCFA
</div>
<br></div></div></div><br>_______________________________________________<br>
Cryptography-dev mailing list<br>
<a href="mailto:Cryptography-dev@python.org">Cryptography-dev@python.org</a><br>
<a href="http://mail.python.org/mailman/listinfo/cryptography-dev" target="_blank">http://mail.python.org/mailman/listinfo/cryptography-dev</a><br>
<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div dir="ltr">"I disapprove of what you say, but I will defend to the death your right to say it." -- Evelyn Beatrice Hall (summarizing Voltaire)<br>
"The people's good is the highest law." -- Cicero<br><div>GPG Key fingerprint: 125F 5C67 DFE9 4084</div></div>
</div>